U.S. patent application number 12/708596 was filed with the patent office on 2011-08-25 for terminals and antenna systems with a primary radiator line capacitively excited by a secondary radiator line.
This patent application is currently assigned to Sony Ericsson Mobile Communications AB. Invention is credited to William H. Darden, IV.
Application Number | 20110206097 12/708596 |
Document ID | / |
Family ID | 44170476 |
Filed Date | 2011-08-25 |
United States Patent
Application |
20110206097 |
Kind Code |
A1 |
Darden, IV; William H. |
August 25, 2011 |
TERMINALS AND ANTENNA SYSTEMS WITH A PRIMARY RADIATOR LINE
CAPACITIVELY EXCITED BY A SECONDARY RADIATOR LINE
Abstract
A communications device can include a radiator structure and a
transceiver circuit. The radiator structure can include a primary
radiator line and a secondary radiator line. The primary radiator
line extends from a RF feed node to a distal end and is configured
to resonant in at least one RF frequency range. The secondary
radiator line extends from the RF feed node to a distal end that is
closely spaced to the primary radiator line to provide capacitive
excitation at a location along the primary radiator line where at
least 70% of a maximum resonant voltage is present in the primary
radiator line while resonating. The transceiver circuit is
configured to encode data according to one or more communication
protocols and to generate a RF signal that is supplied to the RF
feed node to cause the radiator structure to radiate the encoded
data as RF electromagnetic radiation through a wireless air
interface.
Inventors: |
Darden, IV; William H.;
(Cary, NC) |
Assignee: |
Sony Ericsson Mobile Communications
AB
|
Family ID: |
44170476 |
Appl. No.: |
12/708596 |
Filed: |
February 19, 2010 |
Current U.S.
Class: |
375/219 ;
343/700MS |
Current CPC
Class: |
H01Q 1/243 20130101;
H01Q 5/371 20150115; H01Q 9/42 20130101 |
Class at
Publication: |
375/219 ;
343/700.MS |
International
Class: |
H04B 1/38 20060101
H04B001/38; H01Q 1/38 20060101 H01Q001/38; H01Q 9/04 20060101
H01Q009/04 |
Claims
1. An antenna system comprising: a radiator structure comprising a
primary radiator line and a secondary radiator line, the primary
radiator line extends from a RF feed node to a distal end and is
configured to resonant in at least one RF frequency range, and the
secondary radiator line extends from the RF feed node to a distal
end that is closely spaced to the primary radiator line to provide
capacitive excitation at a location along the primary radiator line
where at least 70% of a maximum resonant voltage is present in the
primary radiator line while resonating.
2. The antenna system of claim 1, wherein: the distal end of the
secondary radiator line is closely spaced to the primary radiator
line to provide capacitive excitation at a location along the
primary radiator line where the maximum resonant voltage is present
in the primary radiator line while resonating.
3. The antenna system of claim 2, wherein: the secondary radiator
line extends from the RF feed node to its distal end by a length
corresponding to about a quarter wavelength of one of the resonant
frequencies; and the primary radiator line extends from the distal
end of the primary radiator line to the location where the primary
radiator line is capacitively excited by the distal end of the
second radiator line by a length corresponding to about a half
wavelength of one of the resonant frequencies.
4. The antenna system of claim 1, wherein: the primary radiator
line extends a first length corresponding to a first fractional
value of the wavelength of one of the resonant frequencies from the
distal end of the primary radiator line to the location where the
primary radiator line is capacitively excited by the distal end of
the second radiator line; the secondary radiator line extends from
the RF feed node to its distal end by a second length that
corresponds to a second fractional value of the wavelength of one
of the resonant frequencies; and the first fractional value is
greater than the second fractional value.
5. The antenna system of claim 4, wherein: the first fractional
value is about a half wavelength of one of the resonant frequencies
and the second fractional value is about a quarter wavelength of
one of the resonant frequencies.
6. The antenna system of claim 1, wherein: the primary radiator
line primarily extends from the RF feed node to its distal end in
two directions that are perpendicular to each other; and the
secondary radiator line primarily extends from the RF feed node to
its distal end in two directions that are perpendicular to each
other.
7. The antenna system of claim 6, wherein: the primary radiator
line primarily extends from the RF feed node to its distal end in a
first direction and then a second direction that is perpendicular
to the first direction; and the secondary radiator line primarily
extends from the RF feed node to its distal end in the second
direction and then in the first direction.
8. The antenna system of claim 7, wherein: the primary radiator
line and the secondary radiator line are arranged so that a
greatest spacing between them occurs at a location along the second
radiator line that corresponds to a length corresponding to about
an eighth of a wavelength of one of the resonant frequencies from
the distal end of the second radiator line.
9. The antenna system of claim 1, wherein: the primary radiator
line primarily extends from the RF feed node to its distal end
along a curved path; and the secondary radiator line primarily
extends from the RF feed node to its distal end along another
curved path.
10. A communications device comprising: a radiator structure
comprising a primary radiator line and a secondary radiator line,
the primary radiator line extends from a RF feed node to a distal
end and is configured to resonant in at least one RF frequency
range, and a secondary radiator line that extends from the RF feed
node to a distal end that is closely spaced to the primary radiator
line to provide capacitive excitation at a location along the
primary radiator line where at least 70% of a maximum resonant
voltage is present in the primary radiator line while resonating;
and a transceiver circuit that is configured to encode data
according to one or more communication protocols and to generate a
RF signal that is supplied to the RF feed node to cause the
radiator structure to radiate the encoded data as RF
electromagnetic radiation through a wireless air interface.
11. The communications device of claim 10, further comprising: a
circuit board that includes a conductive ground plane, wherein the
first and second radiator lines conform to a major surface of the
circuit board and do not overlap the conductive ground plane.
12. The communications device of claim 11, wherein the first and
second radiator lines are integrally formed as a single conductive
layer on the circuit board.
13. The communications device of claim 10, further comprising: a
controller circuit; and a display circuit, wherein the transceiver
circuitry, the controller circuit, and the display circuit are
mounted to the circuit board and are grounded to the ground plane,
and wherein the first and second radiator lines are spaced apart
from the controller circuit and the display circuit.
14. The communications device of claim 10, wherein: the distal end
of the secondary radiator line is closely spaced to the primary
radiator line to provide capacitive excitation at a location along
the primary radiator line where the maximum resonant voltage is
present in the primary radiator line while resonating.
15. The communications device of claim 14, wherein: the secondary
radiator line extends from the RF feed node to its distal end by a
length corresponding to about a quarter wavelength of one of the
resonant frequencies; and the primary radiator line extends from
the distal end of the primary radiator line to the location where
the primary radiator line is capacitively excited by the distal end
of the second radiator line by a length corresponding to about a
half wavelength of one of the resonant frequencies.
16. The communications device of claim 10, wherein: the primary
radiator line extends a length corresponding to a first fractional
value of the wavelength of one of the resonant frequencies from the
distal end of the primary radiator line to the location where the
primary radiator line is capacitively excited by the distal end of
the second radiator line; the secondary radiator line extends from
the RF feed node to its distal end by a length that corresponds to
a second fractional value of the wavelength of one of the resonant
frequencies; and the first fractional value is greater than the
second fractional value.
17. The communications device of claim 16, wherein: the first
fractional value is about a half wavelength of one of the resonant
frequencies and the second fractional value is about a quarter
wavelength of one of the resonant frequencies.
18. The communications device of claim 10, wherein: the primary
radiator line primarily extends from the RF feed node to its distal
end in two directions that are perpendicular to each other; and the
secondary radiator line primarily extends from the RF feed node to
its distal end in two directions that are perpendicular to each
other.
19. The communications device of claim 18, wherein: the primary
radiator line primarily extends from the RF feed node to its distal
end in a first direction and then a second direction that are
perpendicular to each other; and the secondary radiator line
primarily extends from the RF feed node to its distal end in the
second direction and then in the first direction.
20. The communications device of claim 19, wherein: the primary
radiator line and the secondary radiator line are arranged so that
a greatest spacing between them occurs at a location along the
second radiator line that corresponds to a length corresponding to
about an eighth of a wavelength of one of the resonant frequencies
from the distal end of the second radiator line.
Description
FIELD OF THE INVENTION
[0001] The invention generally relates to the field of
communications, and more particularly, to antennas that are used by
wireless communication terminals for transmission and
reception.
BACKGROUND OF THE INVENTION
[0002] Wireless terminals may operate in multiple frequency bands
in order to provide operations in multiple communications systems.
For example, many cellular radiotelephones, laptop computers, and
other electronic communication devices are now designed for
pentaband operation in frequency bands that cover, for example,
GSM850 (824-894 MHz), GSM900 (880-960 MHz), DCS (1710-1880 MHz),
PCS (1850-1990 MHz), and UMTS (1920-2170 MHz).
[0003] Achieving effective performance in some or all of the above
described frequency bands (i.e., "multiband") may be difficult.
Contemporary wireless terminals are increasingly packing more
circuitry and larger displays and keypads/keyboards within small
housings. As a consequence, there has been increased use of
semi-planar antennas, such as a multi-branch inverted-F antenna,
that may occupy a smaller space within a terminal housing. The
semi-planar antenna can be printed on/mounted to the terminal's
main printed circuit board, but should be placed away from a ground
plane of the terminal's printed circuit board to be useful.
Constraints on the available space and location for the branches of
the antenna can negatively affect the antenna performance.
SUMMARY
[0004] Embodiments according to the invention can provide multiband
antennas for use in communications device. In some embodiments, a
communications device includes a radiator structure and a
transceiver circuit. The radiator structure can include a primary
radiator line and a secondary radiator line. The primary radiator
line extends from a RF feed node to a distal end and is configured
to resonant in at least one RF frequency range. The secondary
radiator line extends from the RF feed node to a distal end that is
closely spaced to the primary radiator line to provide capacitive
excitation at a location along the primary radiator line where at
least 70% of a maximum resonant voltage is present in the primary
radiator line while resonating. The transceiver circuit is
configured to encode data according to one or more communication
protocols and to generate a RF signal that is supplied to the RF
feed node to cause the radiator structure to radiate the encoded
data as RF electromagnetic radiation through a wireless air
interface.
[0005] In some further embodiments, the communications device
further includes a circuit board that includes a conductive ground
plane. The first and second radiator lines may conform to a major
surface of the printed circuit board and not overlap the conductive
ground plane, although the radiator lines may be spaced apart from
the printed circuit board on, for example, an antenna carrier
structure (e.g., attached to a portion of a terminal housing). The
first and second radiator lines may be integrally formed as a
single conductive layer on the printed circuit board.
[0006] In some further embodiments, the communications device
further includes a controller circuit and a display circuit. The
transceiver circuitry, the controller circuit, and the display
circuit are mounted to the circuit board and are grounded to the
ground plane. The first and second radiator lines are spaced apart
from the controller circuit and the display circuit.
[0007] In some further embodiments, the distal end of the secondary
radiator line is closely spaced to the primary radiator line to
provide capacitive excitation at a location along the primary
radiator line where the maximum resonant voltage is present in the
primary radiator line while resonating. The secondary radiator line
may extend from the RF feed node to its distal end by a length
corresponding to about a quarter wavelength of one of the resonant
frequencies. The primary radiator line may extend from the distal
end of the primary radiator line to the location where the primary
radiator line is capacitively excited by the distal end of the
second radiator line by a length corresponding to about a half
wavelength of one of the resonant frequencies.
[0008] In some further embodiments, the primary radiator line
extends a length corresponding to a first fractional value of the
wavelength of one of the resonant frequencies from the distal end
of the primary radiator line to the location where the primary
radiator line is capacitively excited by the distal end of the
second radiator line. The secondary radiator line extends from the
RF feed node to its distal end by a length that corresponds to a
second fractional value of the wavelength of one of the resonant
frequencies. The first fractional value is greater than the second
fractional value. The first fractional value may be about a half
wavelength of one of the resonant frequencies and the second
fractional value is about a quarter wavelength of one of the
resonant frequencies.
[0009] In some further embodiments, the primary radiator line
primarily extends from the RF feed node to its distal end in two
directions that are perpendicular to each other, and the secondary
radiator line primarily extends from the RF feed node to its distal
end in two directions that are perpendicular to each other. The
primary radiator line may primarily extend from the RF feed node to
its distal end in a first direction and then a second direction
that are perpendicular to each other, and the secondary radiator
line may primarily extend from the RF feed node to its distal end
in the second direction and then in the first direction.
[0010] In some further embodiments, the primary radiator line and
the secondary radiator line are arranged so that a greatest spacing
between them occurs at a location along the second radiator line
that corresponds to a length corresponding to about an eighth of a
wavelength of one of the resonant frequencies from the distal end
of the second radiator line.
[0011] Some other embodiments are directed to an antenna system
that includes a radiator structure. The radiator structure includes
a primary radiator line and a secondary radiator line. The primary
radiator line extends from a RF feed node to a distal end and is
configured to resonant in at least one RF frequency range. The
secondary radiator line extends from the RF feed node to a distal
end that is closely spaced to the primary radiator line to provide
capacitive excitation at a location along the primary radiator line
where at least 70% of a maximum resonant voltage is present in the
primary radiator line while resonating.
[0012] In some further embodiments, the distal end of the secondary
radiator line is closely spaced to the primary radiator line to
provide capacitive excitation at a location along the primary
radiator line where the maximum resonant voltage is present in the
primary radiator line while resonating. The secondary radiator line
may extend from the RF feed node to its distal end by a length
corresponding to about a quarter wavelength of one of the resonant
frequencies. The primary radiator line may extend from the distal
end of the primary radiator line to the location where the primary
radiator line is capacitively excited by the distal end of the
second radiator line by a length corresponding to about a half
wavelength of one of the resonant frequencies.
[0013] In some further embodiments, the primary radiator line
extends a length corresponding to a first fractional value of the
wavelength of one of the resonant frequencies from the distal end
of the primary radiator line to the location where the primary
radiator line is capacitively excited by the distal end of the
second radiator line. The secondary radiator line extends from the
RF feed node to its distal end by a length that corresponds to a
second fractional value of the wavelength of one of the resonant
frequencies. The first fractional value is greater than the second
fractional value. The first fractional value may be about a half
wavelength of one of the resonant frequencies and the second
fractional value is about a quarter wavelength of one of the
resonant frequencies.
[0014] In some further embodiments, the primary radiator line
primarily extends from the RF feed node to its distal end in two
directions that are perpendicular to each other. The secondary
radiator line primarily extends from the RF feed node to its distal
end in two directions that are perpendicular to each other. The
primary radiator line may primarily extend from the RF feed node to
its distal end in a first direction and then a second direction
that are perpendicular to each other. The secondary radiator line
may primarily extend from the RF feed node to its distal end in the
second direction and then in the first direction.
[0015] In some further embodiments, the primary radiator line and
the secondary radiator line are arranged so that a greatest spacing
between them occurs at a location along the second radiator line
that corresponds to a length corresponding to about an eighth of a
wavelength of one of the resonant frequencies from the distal end
of the second radiator line.
[0016] In some further embodiments, the primary radiator line
primarily extends from the RF feed node to its distal end along a
curved path, and the secondary radiator line primarily extends from
the RF feed node to its distal end along another curved path.
[0017] Other antenna systems, communications devices, and/or
methods according to embodiments of the invention will be or become
apparent to one with skill in the art upon review of the following
drawings and detailed description. It is intended that all such
additional antenna systems, communications devices, and/or methods
be included within this description, be within the scope of the
present invention, and be protected by the accompanying claims.
Moreover, it is intended that all embodiments disclosed herein can
be implemented separately or combined in any way and/or
combination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this application, illustrate certain
embodiment(s) of the invention. In the drawings:
[0019] FIG. 1 illustrates a plan view of a multiband antenna system
according to some embodiments of the present invention;
[0020] FIG. 2 illustrates a plan view of another multiband antenna
system according to some other embodiments of the present
invention;
[0021] FIG. 3 illustrates a plan view of another multiband antenna
system according to some other embodiments of the present
invention; and
[0022] FIG. 4 is a functional block diagram of a multiband wireless
communication terminal with a multiband antenna system that is
configured according to some embodiments of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION
[0023] The invention will now be described more fully hereinafter
with reference to the accompanying drawings, in which embodiments
of the invention are shown. This invention may, however, be
embodied in many different forms and should not be construed as
limited to the embodiments set forth herein; rather, these
embodiments are provided so that this disclosure will be thorough
and complete, and will fully convey the scope of the invention to
those skilled in the art.
[0024] It will be understood that, when an element is referred to
as being "coupled" to another element, it can be directly coupled
to the other element or intervening elements may be present. In
contrast, when an element is referred to as being "directly
coupled" to another element, there are no intervening elements
present. Like numbers refer to like elements throughout.
[0025] Spatially relative terms, such as "above", "below", "upper",
"lower" and the like, may be used herein for ease of description to
describe one element or feature's relationship to another
element(s) or feature(s) as illustrated in the figures. It will be
understood that the spatially relative terms are intended to
encompass different orientations of the device in use or operation
in addition to the orientation depicted in the figures. For
example, if the device in the figures is turned over, elements
described as "below" other elements or features would then be
oriented "above" the other elements or features. Thus, the
exemplary term "below" can encompass both an orientation of above
and below. The device may be otherwise oriented (rotated 90 degrees
or at other orientations) and the spatially relative descriptors
used herein interpreted accordingly. Well-known functions or
constructions may not be described in detail for brevity and/or
clarity.
[0026] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of this specification and the relevant art
and will not be interpreted in an idealized or overly formal sense
expressly so defined herein.
[0027] Embodiments of the invention are described herein with
reference to schematic illustrations of idealized embodiments of
the invention. As such, variations from the shapes and relative
sizes of the illustrations as a result, for example, of
manufacturing techniques and/or tolerances, are to be expected.
Thus, embodiments of the invention should not be construed as
limited to the particular shapes and relative sizes of regions
illustrated herein but are to include deviations in shapes and/or
relative sizes that result, for example, from different operational
constraints and/or from manufacturing constraints. Thus, the
elements illustrated in the figures are schematic in nature and
their shapes are not intended to illustrate the actual shape of a
region of a device and are not intended to limit the scope of the
invention.
[0028] For purposes of illustration and explanation only, various
embodiments of the present invention are described herein in the
context of multiband wireless communication terminals ("wireless
terminals" or "terminals") that are configured to carry out
cellular communications (e.g., cellular voice and/or data
communications) in more than one frequency band. It will be
understood, however, that the present invention is not limited to
such embodiments and may be embodied generally in any wireless
communication terminal that includes a multiband RF antenna that is
configured to transmit and receive in two or more frequency
bands.
[0029] As used herein, the term "multiband" can include, for
example, operations in any of the following bands: Advanced Mobile
Phone Service (AMPS), ANSI-136, Global Standard for Mobile (GSM)
communication, General Packet Radio Service (GPRS), enhanced data
rates for GSM evolution (EDGE), DCS, PDC, PCS, code division
multiple access (CDMA), wideband-CDMA, CDMA2000, and/or Universal
Mobile Telecommunications System (UMTS) frequency bands. GSM
operation can include transmission in a frequency range of about
824 MHz to about 849 MHz and reception in a frequency range of
about 869 MHz to about 894 MHz. EGSM operation can include
transmission in a frequency range of about 880 MHz to about 914 MHz
and reception in a frequency range of about 925 MHz to about 960
MHz. DCS operation can include transmission in a frequency range of
about 1710 MHz to about 1785 MHz and reception in a frequency range
of about 1805 MHz to about 1880 MHz. PDC operation can include
transmission in a frequency range of about 893 MHz to about 953 MHz
and reception in a frequency range of about 810 MHz to about 885
MHz. PCS operation can include transmission in a frequency range of
about 1850 MHz to about 1910 MHz and reception in a frequency range
of about 1930 MHz to about 1990 MHz. Other bands can also be used
in embodiments according to the invention.
[0030] Some embodiments may arise from the present realization that
a multiband antenna structure can be configured to use a dual feed
excitation structure that excites a primary radiator line using RF
signals that are supplied by both by galvanic conduction and by
capacitive coupling. The antenna structure may provide improved low
band radiator efficiency by supplying RF signals to the primary
radiator line using galvanic conduction, and may provide improved
high band radiator efficiency by supplying RF signals to the
primary radiator line using capacitive coupling.
[0031] The antenna structure may include at least a primary
radiator line and a secondary radiator line that supplies through
capacitive coupling RF excitation signals to the primary radiator
line. Some embodiments may further arise from the present
realization that the length of the secondary radiator line may
preferably be about a quarter wavelength of the desired high band
resonance frequency of the primary radiator line. Moreover, the
secondary radiator line may preferably be configured to
capacitively excite the primary radiator line at a location that is
about a half wavelength of one of the resonant frequencies from the
distal end of the primary radiator line, which can correspond to
where a voltage maximum occurs during resonance of the primary
radiator line. A maximum transfer of power may occur when a maximum
resonance voltage occurs at both the end of the secondary radiator
line that capacitively excites the primary radiator line and at the
corresponding location along the primary radiator line that is
capacitively excited by the secondary radiator line.
[0032] This structural configuration of the primary and secondary
radiator lines may provide improved broadband excitation efficiency
of the multiband antenna structure across a wider frequency range.
For example, this multiband antenna structure may exhibit higher
radiation efficiency during transmission and, thereby, have higher
Total Radiated Power, lower current drain, and/or increased
communication time and/or battery life for a communications device.
Similarly, during reception, this multiband antenna structure may
provide lower Total Isotropic Sensitivity, which may enable a
communication device to maintain an ongoing call further into a
fringe area of a base station coverage area and/or deeper into a
signal fading environment to avoid dropped calls. Moreover, this
multiband antenna structure may enable improved control and
localization of high band excitation currents and, thereby, reduced
stray currents and fields therefrom and provide improved specific
absorption rate (SAR) and/or hearing aid compatibility (HAC).
[0033] A multiband antenna system that is configured according to
some embodiments of the present invention is shown in FIG. 1.
Referring to FIG. 1, the antenna system includes a radiator
structure 100 that includes a primary radiator line 110 and a
secondary radiator line 120. The primary radiator line 110 extends
from a RF feed node 130 to a distal end 112 and is configured to be
resonated in a plurality of different RF frequency ranges. The
secondary radiator line 120 extends from the RF feed node 130 to a
distal end 122 that is closely spaced to the primary radiator line
110 to provide capacitive excitation at a location 114 along the
primary radiator line 110.
[0034] The secondary radiator line 120 is spaced apart from the
primary radiator line 110 to reduce capacitive coupling
therebetween except from the distal end 122 of the secondary
radiator line 120 to the location 114 along the primary radiator
line 110. Accordingly, as shown in FIG. 1 in accordance with some
exemplary embodiments, the primary radiator line 110 may primarily
extend from the RF feed node 130 to its distal end 112 in a first
direction and then a second direction that are perpendicular to
each other. The secondary radiator line 120 may primarily extend
from the RF feed node 130 to its distal end 122 in the second
direction and then in the first direction.
[0035] The lengths of the primary and secondary radiator lines 110,
120 and the location 114 of the capacitive coupling from the
secondary radiator line 120 to the primary radiator line 110 are
defined to provide improved broadband excitation efficiency of the
multiband antenna structure across one or more desired frequency
ranges. In some embodiments, the radiator structure 100 is
configured to capacitively excite the primary radiator line 110 at
the location 114 where a maximum resonant voltage (Vmax) is present
in the primary radiator line 110 during its RF resonance. The
distal end 122 of the secondary radiator line 120 may therefore be
closely spaced to the primary radiator line 110 at the location 114
where the maximum resonant voltage occurs. The maximum resonant
voltage may occur at a length 116 that corresponds to about a half
wavelength of one of the resonant frequencies from the distal end
112 of the primary radiator line 110. A length 118 from the
capacitive excitation location 114 to the RF feed node 130 can be
adjusted to tune the range of resonant frequencies of the primary
radiator line 110.
[0036] Maximum capacitive excitation may be provided by the
secondary radiator line 120 to the primary radiator line 110 when
the secondary radiator line 120 has a length 124 that provides a
maximum resonant voltage at its distal end 122 that excites the
primary radiator line 110. The secondary radiator line 120 can
therefore function as a transmission line having a length that can
be tuned to maximize its capacitive coupling to the primary
radiator line 110. A maximum resonant voltage may occur at the
distal end 122 of the secondary radiator line when the length 124
from the RF feed node 130 to the distal end 122 is about a quarter
wavelength of one of the resonant frequencies.
[0037] Although various efficiencies and advantages are described
above may be provided by configuring the secondary radiator line
120 to have a length that corresponds to about a quarter wavelength
and the primary radiator line 110 to have a length responding to
about a half wavelength from the capacitive coupling location 114
to its distal end 112, the invention is not limited thereto. The
primary radiator line 110 has a sinusoidal standing wave excitation
waveform and, therefore, the slope is zero at the location of the
maximum voltage and initially decreases gradually with distance
therefrom and then decreases rapidly further away. Accordingly, the
capacitive coupling location 114 can be varied somewhat from the
maximum resonant voltage location of the primary radiator line 110
with what may be an acceptable change in transmission/reception
efficiency of the radiator structure 110. In view of the roll-off
of standing wave voltage in the primary radiator line 110 and the
corresponding affect on the transmission/reception efficiency of
the radiator structure 100, it has been determined that an
acceptable range of transmission/reception efficiency according to
some embodiments may be obtained when the primary radiator line 110
is capacitively excited by the secondary radiator line 124 at a
location where at least 70% of a maximum resonant voltage is
present in the primary radiator line 110 during its RF
resonance.
[0038] Accordingly, the lengths of the primary and secondary
radiator lines 110, 120 and the capacitive coupling location
therebetween can be adjusted to provide certain
transmission/reception efficiency over a deified range of frequency
bands. FIG. 2 illustrates a plan view of another multiband antenna
system which illustrates how various lengths of a radiator
structure 200 can be adjusted according to some embodiments.
Referring to FIG. 2, a primary radiator line 210 may have a length,
from its distal end 212 to the capacitive coupling location 214,
that corresponds to a first fractional value of the wavelength of
one of the resonant frequencies. A secondary radiator line 220 may
have a length 224, from the RF feed node 130 to its distal end 222,
that corresponds to a second fractional value of the wavelength of
one of the resonant frequencies. Because the primary radiator line
210 is configured to be the primary source of RF radiation from the
structure 200, the first fractional value should be greater than
the second fractional value. The first and second fractional values
can be regulated during fabrication to tune the operational
frequency ranges (e.g., low and high resonant frequency range) and
efficiency of the radiator structure 200.
[0039] Although certain advantages, such as maximizing excitation
energy, may be provided when the capacitive coupling location 214
corresponds to a location of the maximum resonant voltage in the
primary radiator line 210, similar advantages may be obtained when
the location 214 corresponds to at least 70% of the maximum
resonant voltage in the primary radiator line 210. Similarly,
certain advantages may be provided when the secondary radiator line
124 is configured to have a maximum resonant voltage at the distal
end 222. For example, similar advantages may be obtained when at
least 70% of the maximum resonant voltage in the secondary radiator
line 220 occurs at the distal 222.
[0040] The radiator structure 100 may be integrally formed on a
rigid or flexible dielectric film surface 150, which is illustrated
as having a dielectric constant .di-elect cons.. For example, the
radiator structure 100 may be deposited or otherwise formed from a
conductive material (e.g. 1 mm width lines) in a pattern on a
circuit board that is spaced apart from a ground plane and other
circuitry of an electronic device. The primary and secondary
radiator lines 110, 120 may be formed from a copper sheet or,
alternatively, may be formed from a copper layer that is deposited
on a flexible dielectric ribbon that is fixedly connected to and
supported by a circuit board and/or various interior surfaces of a
housing of the electronic device. It will be understood that
antennas according to embodiments of the invention may be formed
from other conductive materials and are not limited to copper.
[0041] It will be understood by those skilled in the art in view of
the present description that the radiator structure 100 may be used
for transmitting and/or receiving RF electromagnetic radiation to
support communications in multiple frequency bands. In particular,
during transmission, the primary radiator line 110 resonates in
response to signals received from a transmitter portion of a
transceiver and radiates corresponding RF electromagnetic radiation
into free-space in corresponding frequency bands. During reception,
the primary radiator line 110 resonates responsive to incident RF
electromagnetic radiation received via free-space and provides a
corresponding signal (in their corresponding frequency band) to the
transceiver circuitry. The secondary radiator line 120 may be
similarly configured to resonate for transmission and reception of
RF signals.
[0042] Although the radiator structures 100, 200 in FIGS. 1 and 2
have been shown as having radiator lines that abruptly change
direction, the invention is not limited thereto. One or both
radiator lines may instead follow curved pathways. For example,
FIG. 3 illustrates a plan view of another multiband antenna system
in which a radiator structure 300 includes primary and secondary
radiator lines 310, 320 that have curved changes in direction. The
curved pathways can still provide desired separation between the
primary and secondary radiator lines 310, 320 except at the
capacitive coupling location 314, and may avoid undesirable
spurious RF emissions that can occur along sharp corners of
conductive pathways.
[0043] FIG. 4 is a functional block diagram of a multiband wireless
communication terminal 400 with a multiband antenna system which,
for example, may include the radiator structure 100 of FIG. 1,
according to some embodiments of the invention. Referring to FIG.
5, the terminal 400 can include a circuit board 402 on which a
controller circuit 410, a transceiver circuit 412, a speaker device
420, a display device 422, a user input interface 424 (e.g.
keyboard/keypad), and a microphone 428 may be mounted. The circuit
board 402 may include a ground plane 404 that provides a common
ground circuit for the controller circuit 410, the transceiver
circuit 412, the speaker device 120, the display device 422, the
user input interface 424 (e.g. keyboard/keypad), and/or the
microphone 428.
[0044] The radiator structure 100 may be formed directly on a major
surface of the circuit board 402 and conform thereto. For example,
the primary and second radiator lines 110, 120 may be formed by
patterning the same conductive layer that is used to form the
ground plane 404, or from a layer that is used to form some other
wiring of the circuit board 402. Alternatively, the radiator lines
110, 120 may be on separate layers of a multi-layer structure.
[0045] It may be advantageous to position the radiator structure
100 away from the ground plane 404, such as spaced apart on the
circuit board 402 from the ground plane 404. A dielectric constant
.di-elect cons. of a part 150 of the circuit board 402 on which the
radiator structure 100 is formed can affect the lengths of the
primary and second radiator lines 110, 120 and the associated
location along the primary radiator line 110 that is capacitively
coupled to the secondary radiator line 120. For example, the RF
resonant wavelength of the radiator structure 100 residing on the
circuit board 402 may correspond to the RF resonant wavelength in a
vacuum divided by the square-root of the dielectric constant
.di-elect cons. of the part 150 on which the radiator structure 100
is formed.
[0046] The controller circuit 410 may include a general purpose
processor and/or digital signal processor which can execute
instructions from a computer readable memory that carry out at
least some functionality to enable wireless communications through
the transceiver circuit 412 and the antenna structure 100 to one or
more other wireless communication terminals and/or base stations
according to one or more RF communication protocols. The controller
circuit 410 may functionally operate the speaker 420, the display
422, the user input interface 424, and the microphone 428. The
transceiver circuit 412 may be configured to encode/decode and
transmit and receive RF communications according to one or more
cellular protocols, which may include, but are not limited to,
Global Standard for Mobile (GSM) communication, General Packet
Radio Service (GPRS), enhanced data rates for GSM evolution (EDGE),
code division multiple access (CDMA), wideband-CDMA, CDMA2000,
and/or Universal Mobile Telecommunications System (UMTS), WiMAX,
and/or Long Term Evolution (LTE), and/or according to a WLAN
(802.11) communication protocol and/or Bluetooth communication
protocol, among others.
[0047] The transceiver circuit 412 is configured to amplify and
supply an electromagnetic radiation signal to the feed node 130
within a selected one of a plurality of different frequency ranges
to cause the primary radiator line 110 to resume. The
electromagnetic radiation signal from the transceiver circuit 412
may be conducted to the feed node 130 through a coaxial cable, a
flex line, and/or a conductive trace on the printed circuit board
402. The transceiver circuit 412 may be further configured to
selectively amplify and supply a signal that is received by the
primary radiator line 110 from another communication terminal/base
station to the controller circuit 410. To facilitate effective
performance during transmission and reception, the output/input
impedance of the transceiver circuit 412 can be "matched" to an
impedance of the antenna structure 100 between the feed node 130
and a ground node to maximize power transfer between the
transceiver circuit 412 and the antenna structure 100. It will be
understood that, as used herein, the term "matched" includes
configurations where the impedances are substantially electrically
tuned to compensate for undesired antenna impedance components to
provide a particular impedance value.
[0048] Many alterations and modifications may be made by those
having ordinary skill in the art, given the benefit of present
disclosure, without departing from the spirit and scope of the
invention. For example, antennas according to embodiments of the
invention may have various shapes, configurations, and/or sizes and
are not limited to those illustrated. Therefore, it must be
understood that the illustrated embodiments have been set forth
only for the purposes of example, and that it should not be taken
as limiting the invention as defined by the following claims. The
following claims are, therefore, to be read to include not only the
combination of elements which are literally set forth but all
equivalent elements for performing substantially the same function
in substantially the same way to obtain substantially the same
result. The claims are thus to be understood to include what is
specifically illustrated and described above, what is conceptually
equivalent, and also what incorporates the essential idea of the
invention.
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